Apple has also reconfigured three and four finger gestures in Lion (which do require a newer trackpad capable of registering more than two fingered touch points).

Previously, three fingered gestures were used to drag windows without having to click on them (although this only worked when targeting the window's menu bar). A secondary option allows for multitouch navigation (such as swiping between album photos).

Both of those previous options are still there in Lion, but the default option for three finger swipes now invokes F9 Mission Control when made upward, or F10 single app windows Exposé when made downward.

When made side to side, three finger swipes pull in Dashboard from the left, or swipe through active Spaces to the right (including any active Full Screen apps). Each Space smoothly animates in from the right or left (shown mid-swipe, below).

Four fingered swipes formerly invoked F9 upward and F11 show desktop downward. The default setting in Lion developer builds now sets four finger swipe to the same settings as three fingers, described above. Also, the four finger swipe side to side in Snow Leopard formerly brought up the App Switcher, but now it swipes in Dashboard or Spaces, a faster way to rapidly move between open, Full Screen apps.

Another new four finger gesture actually works best with five fingers: pinching all your fingers together now invokes Launchpad, the new Mac analog of the iOS Home page of launchable app icons. Expanding your fingers back out dismisses Launchpad and returns you to the desktop. From the desktop, spreading four or five fingers out performs an F11 "hide all windows/show desktop."

All of these gestures feel more intuitive and sensible, but it's not clear why three and four fingered gestures are set to perform the same task (although both can be reconfigured to perform different tasks to the preference of the user; this wasn't the case in Snow Leopard).